Artery of Percheron infarction results in severe bradycardia: A case report.

BACKGROUND: The thalamus is normally supplied by each posterior cerebral artery (PCA). The artery of percheron is a variant of this anatomy as it arises as a single trunk unilaterally from the PCA to supply the thalamus bilaterally. Occlusion of this artery is rare, and the diagnosis is usually missed without obtaining an MRI. CASE DESCRIPTION: We illustrate the case of a 68-year-old male who presented with coma, ocular gaze palsy, and severe bradycardia from bilateral thalamic nuclei and midbrain infarction, as described as an artery of Percheron infarction. The patient recovered neurologically under conservative treatment with a residual vertical diplopia from downward gaze palsy. He underwent cardiac pacer implantation for severe bradycardia at the end of his admission. The thalamic pathway associated with cardiac rhythm, especially the zona inserta, is discussed. Publications related to the artery of Percheron are reviewed. CONCLUSION: Coma and ocular gaze palsy are the most common presentations following thalamic and midbrain ischemia from artery of Percheron infarction. To our knowledge, only a single case of artery of Percheron infarction with severe bradycardia has been reported in the past. Our case attested the role of thalamic nuclei controlling cardiac rhythm.

Iridescence impairs object recognition in bumblebees.

Iridescence is a taxonomically widespread and striking form of animal coloration, yet despite advances in understanding its mechanism, its function and adaptive value are poorly understood. We test a counterintuitive hypothesis about the function of iridescence: that it can act as camouflage through interference with object recognition. Using an established insect visual model (Bombus terrestris), we demonstrate that both diffraction grating and multilayer iridescence impair shape recognition (although not the more subtle form of diffraction grating seen in some flowers), supporting the idea that both strategies can be effective means of camouflage. We conclude that iridescence produces visual signals that can confuse potential predators, and this might explain the high frequency of iridescence in many animal taxa.